This invention relates to a process for making an isoflavone concentrate product from soybeans. Isoflavones are a unique class of phytoestrogens--plant hormones--that naturally occur in soybeans.
It is anticipated that consumer demand for soy isoflavones will continue to grow. Scientists have demonstrated that isoflavones have the ability to inhibit cancer cell growth, and some researchers believe that isoflavones may contribute to soy's ability to lower blood-cholesterol levels.
The principal types of isoflavones found in soybeans are glucones (with sugars) and aglucones (without sugars). Glucones have the glucose molecule attached, and include genistin, daidzin and glycitin. Aglucones are isoflavones without the glucose molecule, and they include genistein, daidzein and glycitein.
The prior art teaches isolating genistin from hexane-extracted soybean flakes. Walter ("Genistin (an Isoflavone Glucoside) and Its Aglucone, Genistein, from Soybeans," J. of Am. Chem. Soc., 63, 3273 (1941)) describes a method involving, among other steps, extracting the flakes with methanol, precipitating with acetone and recrystallizing with ethanol.
U.S. Pat. No. 5,141,746 (Fleury et al.) describes a method for preparing an impure extract of two specific isoflavones daidzin malonate and genistin malonate. Fleury describes a method involving, among other steps, mixing hexane-defatted ground soybeans with 80 percent (%) aqueous methanol, filtering and drying; adjusting pH multiple times with, among other chemicals, hydrochloric acid and sodium hydroxide, and extracting with an organic solvent, such as butanol.
U.S. Pat. No. 5,352,384 (Shen) describes making an aglucone enriched fiber. Shen describes solubilizing isoflavones from soy flour by, among other steps, forming a slurry with an extractant, such as sodium, potassium or calcium hydroxide, to adjust the pH to the proteins' isoelectric point of 6.7-9.7, and reacting the slurry with the enzyme beta-glucosidase.
The use of multiple acids/bases and organic solvents to extract isoflavones from soybeans makes it costly to commercially manufacture soy isoflavone products. The use of a number of materials to extract isoflavones, not only increases raw material, equipment and labor costs, but also creates significant safety and environmental concerns.
It is apparent that an efficient process for removing isoflavones from soybeans is needed. It also is apparent that a low-cost soy isoflavone concentrate (SIC) product is needed.